1. Field of the Invention
The present invention relates to an image forming apparatus such as printers, facsimiles and copiers using electrophotographic image forming methods, and more particularly to a toner feeder, a toner, and an electrophotographic image forming apparatus using the toner feeder and toner.
2. Discussion of the Background
For example, the following toner feeding methods are conventionally known:
(1) a method of feeding a toner with a coil screw arranged in a pipe formed between a sender and a receiver; (2) a method of feeding a toner mostly by gravity while closely locating a sender and a receiver above and below; and (3) a method of feeding a toner from a sender to receiver optionally located through a pipe with a pressure applied by a powder pump as disclosed in, e.g., Japanese Laid-Open Patent Publications Nos. 2002-139906 and 2002-139902.
Each of the above-mentioned methods (1) and (2) are significantly limited by the relative position of the sender and receiver, and have many disadvantages, e.g., not suitable for a long-distance feeding. Now, the above-mentioned toner feeding method (3) has fewer problems and attracts attention. Particularly, as an electrophotographic image forming apparatus has a toner container with a larger volume, the toner feeding method (3) permits more freedom for layout and saves space in a place where the electrophotographic image forming apparatus is used. Particularly, a full-color electrophotographic image forming apparatus using four color toners and the toner feeding method (3) has an advantage in terms of the layout and space-saving.
However, even the toner feeding method (3), because a sender and a receiver are connected with a pipe, etc., a toner blockage in the pipe may occur. When the toner blockage occurs, a toner cannot be fed, resulting in a serious problem for a whole system. Thus, the pipe is shortened to prevent occurrence of the toner blockage, resulting a limitation to the layout freedom. In addition, the toner feeding method (3) has an unstable toner feeding speed, resulting in complicated control thereof. Further, when the toner passes through the powder pump, the toner deteriorates due to a friction therewith and produces foggy images.
Consequently, there is still need for a toner feeder, a toner and an electrophotographic image forming apparatus using the toner feeder and toner, which permit a larger layout freedom and simply control feeding a stable amount of a toner without toner blockage.